Macrophages are prominent in the histopathology of emphysema and other chronic inflammatory processes characterized by excessive connective tissue turnover. The overall objective of this proposal is to define the role of lung macrophages in the pathobiology of smoking-related chronic lung disease. Recent cloning of all four of the known eukaryotic cysteine proteases has identified one of these, human cathepsin S, as an elastase. Cathepsin S has been found to have appreciable elastase activity at both acidic and neutral pH. Evidence indicates that alveolar macrophages from smokers have increased activity over those of nonsmoker cells of cathepsin S. This macrophage elastase activity is inducible in vitro by co-culture of live cells with elastin and potentially regulated by two endogenous inhibitors secreted by these same cells, TIMP and cystatin C. Experiments are directed toward the central hypothesis that dysregulation of macrophage elastase activity -- inducible by cigarette smoking -- is an important determinant of lung injury. In order to test this hypothesis antibodies to recombinant human cathepsin S will be raised to assist in further purification and characterization of the enzyme. The mechanism of increased cathepsin S activity in smoker macrophages will be examined and whether cysteine proteases exist on the macrophage cell surface defined by immunologic and electron microscopic techniques. the influence of extracellular matrix proteins, elastin receptors, and cytokines on the expression of macrophage cathepsins S and L, as well a the 92-kDa gelatinase, will be studied by mRNA and functional assays in vitro. The functional importance of cystatin C and TIMP in regulating matrix metabolism by macrophages will be assessed, in part, by partially blocking cystatin C and TIMP biosynthesis with antisense oligonucleotides and measuring the effects on extracellular matrix degradation by macrophages. Finally, macrophage expression of cathepsins S and L, the 92-kDa gelatinase, and the inhibitors TIMP and cystatin C will be examined in alveolar macrophages obtained from cigarette smokers with normal or reduced lung function (FEV1/FVC). These experiments should elucidate the molecular process by which human macrophages degrade elastin, define its regulation in vitro, and directly test whether altered enzyme and/or inhibitor expression by macrophages is implicated in the pathobiology of smoking-related lung disease. The results should provide a clearer view of the role of macrophages in emphysema and a sound foundation for future efforts both to monitor and to modulate macrophage proteolysis in vivo.